1. Field of the Invention
The present invention relates to a process for the production of oxygen-containing compounds by the oxo process by reacting olefinic hydrocarbons with carbon monoxide and hydrogen, said process permitting an improved conversion of the starting materials.
2. Discussion of the Prior Art
The oxo synthesis or hydroformylation is conventionally carried out in a high pressure tubular reactor as a liquid phase process. The liquid phase consists of the oxo product and olefin dissolved therein. Olefin, synthesis gas and a suitable metal compound such as compounds of cobalt or rhodium in solution or suspension are added in controlled amounts at the base of the reactor. In the reactor which is operated within wide ranges of pressure and temperature, e.g. at about 5 to 1000 bar and 50.degree. to 200.degree. C., e.g. with the use of cobalt as the catalyst at 200 to 300 bar and 130.degree. to 180.degree. C., the corresponding carbonyl or hydrocarbonyl which catalyzes the hydroformylation is formed from the metal compound. The reaction product which is a mixture of oxygen-containing compounds and unreacted starting materials leaves the reactor at the top and is cooled in a downstream of the reactor to a temperature at which reaction no longer takes place. Thereafter, the mixture is fed to a high pressure separator in which the separator into the liquid phase and gaseous phase takes place. In addition, it is the purpose of the gas separator to ensure that the reaction product flows uniformly from the reactor system. The gas leaving at the top of the separator may be admixed with the fresh gas and reintroduced to the reactor. The liquid phase is withdrawn at the base of the separator and thereafter depressurized into a catalyst decomposition vessel. The liquid level in the gas separator is maintained constant by appropriate control apparatus.
Various process for converting the olefin charged to the oxo synthesis as far as possible into the desired reaction products have been proposed.
According to the disclosure of German Pat. No. 935,126, the oxygen-containing compounds obtained in the first reaction stage are separated from the unreacted reaction mixture and then at least part of this mixture containing an unsaturated olefinic compound is reacted with carbon monoxide and hydrogen in at least one subsequent reaction stage to form oxygen-containing organic compounds.
In the process disclosed in U.S. Pat. No. 2,557,701, maximum conversion of olefin is achieved by returning the oxo raw product under the oxo reaction pressure from the high pressure separator to the reactor and readily mixing the gas and liquid streams in a controlled manner by subdividing the reactor in separate chambers.
In the variant of the process described in German Offenlegungsschrift (DE-OS) No. 2,263,498, the reaction is carried out in a reactor consisting of two or three chambers which are series-connected in such a manner that the gas and liquid streams are passed in a predetermined direction. Olefin conversions of more than 99% can be obtained by this measure.
A two-stage process for hydroformylating olefins is disclosed in German Offenlegungsschrift (DE-OS) No. 25 38 037. In this process, the hydroformylation is carried out in a first stage to a conversion of 40 to 75% depending upon the reaction mixture and then, in a second stage, to a conversion of at least 95% and preferably 95 to 98% without backmixing.
All of the processes mentioned above suffer from the disadvantage that they require high apparative outlay. Either special reactor designs are necessary or additional process steps must be included.
On the other hand, an attempt to increase the olefin conversion by high amounts of catalyst or increase in reaction temperatures results in increased information of undesirable higher boiling compounds. In addition, hydroformylation of propylene under these conditions results to an increased extent in iso compounds which can hardly be commerically utilized.
Accordingly, it is an object of the present invention to provide a process which permits olefin conversions of more than 99% to be achieved with additional process steps and with the use of reactors of as simple a design as possible.
In addition, it is an object of the invention to provide a process capable of being used not only in new plants but also in existing plants which are already in operation without their being extensively rebuilt.